An example of a valve for controlling differential flows and pressures is shown in U.S. Pat. No. 4,005,733 entitled Pressure Control Valve issued to John W. Riddel. The valve has a pair of axially spaced inlets in flow communication with a chamber; the chamber, in turn, is in fluid communication with a consumer for the pressurized fluid and flow. Pressure in the chamber or flow through the chamber is varied by an oscillating valve member which is movable to a first position which closes one inlet and opens the other and movable to a second position which opens the other inlet and closes the first inlet. The valve is solenoid operated and includes a valve member which acts as the solenoid armature. The solenoid armature is disposed entirely within the control chamber.
Another example of a high frequency valve is shown in U.S. Pat. No. 3,661,183 entitled Electromagnetically Operated Valve with Two Seats issued to Komaroff et al. In this valve, the valve member is disposed in a control chamber between two seats. Movement of the valve member results (in one direction) from a force exerted by an armature. The armature extends into the control chamber and is pressed against the valve member by a spring. Thus, the spring holds the valve member against one seat. The armature is retracted to a disengaged position from the valve member by a solenoid to allow fluid pressure to float the valve member to the other seat. As does the valve shown in U.S. Pat. No. 4,005,733, operation of this valve depends upon the pressure of the fluid at one port urging the valve member into engagement with the opposing valve seat.
The above art notwithstanding, scientists and engineers are seeking to develop a valve assembly which is operable at high frequency either mechanically or electromagnetically between two opposed seats and which is adapted to provide a variable pressure from a control chamber.